Digital polarimetric system for generating polarization agile signals

Abstract

A digital polarimeter employs a signal time stretching technique to apply polarization phase shift characteristics to digitally generated polarization agile signal components. An RF signal to be transmitted is down-converted to an intermediate frequency and digitally sampled at a rate feasible with currently-available analog-to-digital converters. Horizontal and vertical signal components of the sampled IF signal are generated by processing the digital signal samples. Each digital signal sample is “time stretched” by storing each sample in M memory locations, such that N samples occupy M×N memory locations. Because each sample is stored in M memory locations, each incremental phase shift from one memory location to the next corresponds to 1/M of the actual sampling interval. The stretching process effectively increases the digital sampling frequency, yielding sufficient phase resolution. The time-stretched signal components are subsequently compressed, converted to analog signals and up-converted for transmission.